Synthesis of pyrazole, thiophene, pyridine and coumarin derivatives
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126.3, 127.6, 128.2, 129.4 (C6H5, C6H4), 164.6 (CO), 172.6 (C=N); Anal. calcd for C19H18N2O3:
C, 70.79; H, 5.63; N, 8.69%. Found: C, 70.82; H, 5.73; N, 8.59%. MS: m/z: (%) 322 (M+, 83%).
Ethyl 2-(1H-benzo[d]imidazol-2-yl)-3-(4-chlorophenyl)acrylate (7c). Yellow crystals from
ethanol; yield: 2.61 g (80%); m.p. 103 oC. IR, : 3477-3349 (NH), 3054 (CH aromatic), 2933,
2863 (CH3, CH2), 1689 (C=O), 1644 (C=N), 1631 (C=C). 1H-NMR: : 1.14 (t, 3H, J = 7.27 Hz,
CH3), 4.21 (q, 2H, J = 7.27 Hz, CH2), 6.24 (s, 1H, CH=C), 7.24-7.39 (m, 8H, 2 C6H4), 8.29 (s,
1H, NH, D2O exchangeable). 13C NMR (DMSO): 16.3 (ester CH3), 52.2 (ester CH2), 89.5, 90.1
(CH=C), 120.3, 122.7, 124.8, 125.2, 126.4, 127.4, 127.9, 128.3, 128.6 (C6H5, C6H4), 164.5
(CO), 172.4 (C=N); Anal. calcd for C18H15ClN2O2: C, 66.16; H, 4.63; N, 8.57%. Found: C,
66.09; H, 4.83; N, 8.59%. MS: m/z: (%) 326 (M+, 60%).
General procedure for the synthesis of the pyrazole derivatives 9a-c
To a solution of either compound 7a (3.22 g, 0.01 mol) with either of hydrazine hydrate (0.50 g,
0.01 mol) or phenylhydrazine (1.08 g, 0.01 mol) or compound 7c (3.26 g, 0.01 mol) with
hydrazine hydrate (0.50 g, 0.01 mol) was added. The reaction mixture, in each case, was heated
under reflux for 6 h then poured onto ice/water mixture containing few drops of hydrochloric
acid and the formed solid product was collected by filtration.
4-(1H-Benzo[d]imidazol-2-yl)-5-phenyl-1H-pyrazol-3-ol (9a). Light brown crystals from
o
ethanol; yield: 2.32 g (84%); m.p. 106 C. IR, : 3569-3329 (OH, 2NH), 3055 (CH aromatic),
1
1644 (C=N), 1630 (C=C). H-NMR: : 7.27-7.42 (m, 9H, C6H5, C6H4), 8.27, 8.31 (2s, 2H,
2NH, D2O exchangeable), 10.28 (s, 1H, OH, D2O exchangeable). 13C NMR (DMSO): 142.6,
143.8 (pyrazole C-4, C-5), 119.8, 120.5, 122.8, 123.6, 124.1, 124.5, 126.8, 127.1, 129.4, 130.6
(C6H5, C6H4), 172.6, 176.2 (2C=N); Anal. calcd for C16H12N4O: C, 69.55; H, 4.38; N, 20.28%.
Found: C, 69.73; H, 4.51; N, 20.37%. MS: m/z: (%) 276 (M+, 38%).
4-(1H-Benzo[d]imidazol-2-yl)-5-(4-chlorophenyl)-1H-pyrazol-3-ol (9b). Light brown crystals
o
from ethanol; yield: 2.45 g (79%); m.p. 208-211 C. IR, : 3523-3321 (OH, 2NH), 3055 (CH
aromatic), 1646 (C=N), 1630 (C=C). 1H-NMR: : 7.22-7.39 (m, 8H, 2C6H4), 8.29, 8.33 (2s, 2H,
2NH, D2O exchangeable), 10.26 (s, 1H, OH, D2O exchangeable). 13C NMR (DMSO): 143.9,
142.4 (pyrazole C-4, C-5), 119.6, 120.8, 123.3, 123.9, 124.2, 124.8, 126.8, 128.9, 129.4, 130.8
(C6H5, C6H4), 176.4, 172.5 (2C=N); Anal. calcd for C16H11ClN4O: C, 61.84; H, 3.57; N, 18.03%.
Found: C, 61.95; H, 3.84; N, 17.89%. MS: m/z: (%) 310 (M+, 30%).
4-(1H-Benzo[d]imidazol-2-yl)-1,5-diphenyl-1H-pyrazol-3-ol (9c). Yellow crystals from 1,4-
dioxane; yield: 2.32 g (66%); m.p. 152-154 oC. IR, : 3520-3349 (OH, NH), 3053 (CH
aromatic), 1642 (C=N), 1633 (C=C); 1H-NMR: : 7.26-7.37 (m, 14H, 2C6H5), 8.25 (s, 1H, NH,
D2O exchangeable), 10.29 (s, 1H, OH, D2O exchangeable). 13C NMR (DMSO): 144.2, 142.6
(pyrazole C-4, C-5), 119.9, 120.3, 123.1, 123.6, 124.1, 124.3, 125.2, 125.3, 126.2, 126.8, 127.0,
127.6, 128.2, 130.8 (C6H4, 2C6H5), 176.2, 172.7 (2C=N); Anal. calcd for C22H16N4O: C, 74.98;
H, 4.58; N, 15.90%. Found: C, 75.22; H, 4.72; N, 15.73%. MS: m/z: (%) 352 (M+, 21%).
Ethyl 1-amino-2-cyano-3-phenylbenzo[4,5]imidazo[1,2-a]pyridine-4-carboxylate (11)
To a solution of compound 6a (3.33 g, 0.01 mol) in ethanol (40 mL) containing triethylamine
(0.50 mL), malononitrile (0.66 g, 0.01 mol) was added. The reaction mixture was heated under
reflux for 6 h then poured onto ice/water mixture containing few drops of hydrochloric acid and
the formed solid product was collected by filtration. Yellow crystals from 1,4-dioxane; yield:
2.42 g (80%); mp: 82 oC. IR, : 3488-3343 (NH2), 3056 (CH aromatic), 2927, 2860 (CH3, CH2),
2225 (CN), 1687 (CO), 1640 (C=N), 1636 (C=C). 1H-NMR: : 1.15 (t, 3H, J = 6.89 Hz, CH3),
Bull. Chem. Soc. Ethiop. 2018, 32(3)